The material handling industry utilizes a variety of mechanisms to lift, move, and place materials such as scrap or finished products. For relocating magnetic materials, e.g., diamagnetic metals, paramagnetic metals, and ferromagnetic metals; an electromagnet is preferable in many cases because it does not require personnel to position the chains, hooks, and other mechanical grasping mechanisms often utilized during the attachment and release of the magnetic material. Such grasping mechanisms can further mar metal surfaces and increase the possibility of product damage.
One drawback to using an electromagnetic lifting device is that the magnetic material may not be readily released by the electromagnet when its power source is removed. For instance, when the power source to the electromagnet is removed, the magnetic material will not immediately be released, but will eventually drop due to the force of gravity. As such, it is common to temporarily reverse the polarity of the electromagnet to repel or “push” the magnetic material from the electromagnet. The magnitude of the reverse charge can be significant and as a result, some magnetic materials—e.g., ferromagnetic—may be re-attracted to the now oppositely charged electromagnet and not drop; or if released, will retain an undesired residual magnetism.
An additional concern when using an electromagnetic lifting device is the discharge and consumption of any power stored within the device after lifting and/or dropping a magnetic material. Any power stored within the device must be discharged and consumed before a generator circuit can be opened and/or reversed to drop a lifted material or pick up a new piece of material. Such is particularly true if DC power is provided to the generator because of the known destructive issues of DC power circuit interruption. As such, it would be advantageous to develop a method which quickly and efficiently discharges and consumes all power stored in the field generator allowing in a manner which fully eliminates any concerns associated with the interruption of a DC power circuit.
The present invention is provided to solve these and other issues.